1. Field of the Invention
The invention relates to the field of mops and the like, having a mop head including a compressible mass or block of material engaged in a channel-shaped carrier by which the mop head is mounted on an elongated handle to form a mop, especially a sponge mop. The invention concerns the particular structure and method steps by which the mop head, and the operative absorbent mop material attached to or integral with the compressible mass, are attached to a carrier channel, and in turn to the handle.
The carrier channel of the invention preferably comprises an integral piece of molded polymer, elongated to correspond substantially to a length of the compressible mass. The carrier defines an open channel between lateral sides that are inclined inwardly and engage the compressible mass at a nip, preferably formed between opposed turned-in lips that can taper to a point. Portions of the compressible mass on either side of the nip (either enclosed in the open channel, or outside the channel and exposed for mopping action) are expanded to a width greater than that of the nip, which locks the compressible mass in the channel. At the nip the mass is substantially compressed. Preferably, portions of the mass inside the channel remain somewhat compressed relative to a rest-state of the mass, while portions outside the channel and remote from the nip fan out to nearly the rest-state of the mass.
The invention also concerns a method of making a mop head from a compressible mass of mop material and a polymer channel as described. The polymer channel is formed to substantially rigid shape prior to its engagement on the mass. Unlike metal channels used for known sponge mops, the polymer channel of the invention is preformed, not ductile, and only minimally deformable if at all. The polymer channel of the invention is not shaped after the sponge or other compressible mass is inserted, as in the prior art, wherein side flanges of ductile metal channels are bent inwardly to squeeze the compressible mass to form the nip. According to the invention, the mop head is assembled by first applying a substantial compressive force against the sides of the mass of mop material, and then applying a driving force between the compressed mop material and the channel, to force the compressed mop material into the channel of the carrier. The mop material can be driven because it is compressed, and expands in the channel beyond the nip. The substantially rigid polymer channel forms a superior means for ensuring a secure engagement by the nip as well as a superior structure for the attachment of an elongated handle.
2. Prior Art
U.S. Pat. No. 2,224,462--Williams and U.S. Pat. No. 4,077,083--Siemund et al. are representative of conventional mop heads and methods for making the same. FIGS. 1-5 herein, labeled "prior art," show the structures and steps involved in making a mop head 20. The Williams patent is typical.
FIG. 5 is an end view of a finally assembled conventional mop head 20, with a metal-channel carrier 22 engaging on a block of sponge 24 that forms the absorbent mop material to be manipulated manually via an elongated handle (not shown). Carrier 22 and the handle are threaded or otherwise connectable. The metal channel 22 is ductile, and the side flanges 26 of the channel are formed to a relatively open configuration as shown in FIGS. 1 and 4, before the block of sponge or other compressible material is inserted. During the assembly process, flanges 26 are bent laterally inwardly, such that as assembled channel 22 is bent closed as shown in FIG. 5. Thus the block of sponge material 24 initially is expanded to its rest state as shown in FIGS. 2 and 3, and after assembly is compressed as in FIG. 5.
The flanges 26 preferably are preformed with inwardly folded lips 42, or lips 42 can be folded inward during the process of bending the ductile flange material inwardly against the sponge. FIG. 4 shows sponge material 24 in a state of compression between the rest state of FIGS. 2 and 3, and the partly compressed state of FIG. 5. In the expanded position of FIG. 2, the sponge material 24 typically is a rectangular block with opposite sides 28 that define its height and a top 32 that defines its width, e.g., about twice the height of the sidewalls 28.
The object is to provide a form of dovetail-like joint whereby the sponge is locked into the channel and cannot readily be extracted from the channel by forces tending to pull the sponge downwardly relative to the channel in FIG. 5. Such forces may occur in use, when the sponge is moved back and forth against a floor or the like, which tends to roll the sponge left and right as shown in FIG. 5. This could cause displacement of the sponge in the carrier and/or damage as lips 42 cut into the sponge. Such forces may also occur, for example, if the mop head is used in a roller mop with movable opposed rollers (not shown) that squeeze inwardly and are displaced downwardly against the lower part of the sponge for wringing.
In FIG. 3, the top wall 32 and portions of the sidewalls 28 of the sponge block are reinforced with a glued-on fabric sheet 34. The glue preferably is soaked into the sponge to a desired depth (indicated by shading 36). Before the glue sets firmly, sponge 24 can be wetted (not shown) to make it highly elastic, and squeezed to drive out excess water, whereupon the sponge and carrier channel are attached.
By FIG. 4, the top wall 32 of the sponge 24 has been pressed up into the open channel 38 defined by the carrier 22, through a throat defined between inturned lips 42. Flanges 26 in FIG. 4 are shown in their relatively more open position. Sponge 24 is slightly constricted between lips 42 of the carrier 22, such that the sponge 24 defines a waist 44 between its sidewalls 28. However, the constriction is not sufficient to substantially resist insertion of the sponge and is inadequate to form a secure joint. The sponge is pressed upwardly against the end of the channel and resides against the end of the channel but for any intervening glue. The waist 44 in FIG. 4 is about one-half the width of the top wall 32 in the rest state shown in FIG. 3.
Channel 22 is ductile sheet metal. Flanges 26 can be bent inwardly by lateral compression, slightly beyond the position shown in FIG. 5, and released to occupy the positions in FIG. 5. The bending can occur at the lateral corners of the channel, about 40.degree.-45.degree. in the arrangement shown, or the flanges can be bent generally into a more rounded dovetail shape. In any event, lips 42 are caused to further constrict waist 44 of sponge 24. The waist 44 is reduced by a factor of four or more relative to the width of the top surface 32 in the expanded position of FIGS. 2 and 3. The sponge 24 is retained in the carrier 22 partly by a pinching action of the inturned lips 42, partly by an adhesive bond between the glue and the carrier 22, and partly because hardening of the shaded region 36 forms a relatively more solid wedge-shaped plate, which resists the tendency of the sponge to come free of the carrier 22, in the manner of a dovetail joint.
Another manner of shaping and making a mop head is disclosed by U.S. Pat. No. 4,077,083. This mop head likewise comprises a carrier and a rectangular block of mop material having four elongated sides extending between spaced ends. However, each side has an elongated slit extending between the spaced ends, which slit defines a midline in each side. The carrier has an inverted-U shape defined by a top wall and two sidewalls. Each sidewall has a bottom edge formed with an inturned lip which projects inwardly, substantially toward the one other inturned lip. The free edges of the lips have enlargements such as wedges or barbs.
The method of making the mop head disclosed by U.S. Pat. No. 4,077,083--Siemund et al includes attaching a block of mop material to a carrier using barbed lips engaged in slits in the sides of uncompressed mop material. This evidently is accomplished either by sliding the carrier and mop material endwise relative to each other, or by forcibly pressing the mop material into the carrier until the mop material above the slit clears the barbed lips. This mop head is unlike Williams in that the carrier sidewalls are not bent as a part of the assembly operation.
It is advantageous if the mop material is held securely in the carrier and protected against damage from the lips in use. Siemund's arrangement is not apt for these purposes, due to the preliminary slitting of the sponge, the relative freedom of the uncompressed sponge to become displaced and to chew against the lips, and other factors. This form of mop also is particularly inapt for use with a wringing structure as in Williams.
Assemblies from bent-together flanged channels as in Williams are relatively secure, but are expensive. Metal is a relatively expensive material. Cutting and forming the metal initially to form an open channel, and then to bend the flanges inwardly, are expensive manufacturing steps and require good quality control. The requirements for protective fabric and glue add to the expense. The resulting sheet metal carrier is not optimal for achieving connection of a handle, and may necessitate various ears, channels, nut and bolt connections and the like for handle couplings (See, e.g., U.S. Pat. No. 4,908,901--Torres), especially if a wringing assembly is included.
It would solve a number of the problems with metal channel carriers if the carriers could be made instead from a more economical material, like a polymer. However, polymer materials are not ductile and cannot be formed in the same manner as metal materials. It might be possible to use a thermoplastic polymer and to heat the polymer during assembly and then cool it, or perhaps to cure a thermoset or thermoplastic polymer while holding it in the required shape on a compressed sponge, these possibilities are impractical and likely to be characterized by worse problems than metal channels.